This application claims priority from German application No. 19853545.7, filed Nov. 20, 1998.
1. Field of the Invention
The present invention relates to a flexible pipe with high dimensional stability, good recovery performance and good resistance to media, and whose inner region is composed of a material with only small amounts of extractable materials. In the present text, the term xe2x80x9cpipexe2x80x9d includes the term xe2x80x9chosexe2x80x9d.
2. Description of the Background
For many applications, for example, in the automotive sector, pipes of high flexibility are demanded. Examples of such pipes include screen wash systems, which are frequently produced from plasticized PVC (G. Walter, Kunststoffe und Elastomere in Krafifahrzeugen, Verlag W. Kohlhannner, Stuttgart, Germany, 1985, pages 187 ff.). Over prolonged periods of use, however, this material loses plasticizer by extraction and/or evaporation and as a result becomes inflexible and embrittles, and tends to form stress cracks. In addition, the PVC is not adequately resistant to greases, oils and fuels. A further disadvantage of pipes produced from PVC is that they do not have a satisfactory capability of bonding to the other components in the system.
The combination of properties demanded for applications of this type of high flexibility and resistance to breaking when flexed, good dimensional stability, good recovery performance, good resistance to media (in particular with respect to greases, oils and fuels) and also good capability to bond to the other components in the system, has hitherto been best obtained with polyether block amides. However, in practice it has always been found that the aqueous-alcoholic media conveyed in pipes of this type extract constituents from the pipe material. The constituents which are dissolved then lead to nozzle blockages or to deposits and/or visual defects after evaporation of the wash liquid on the wetted surfaces. A need, therefore, continues to exist for a pipe which exhibits improved stability and contains a lower proportion of extractible components
Accordingly, one object of the present invention is to provide a molding composition, which is particularly useful for the preparation of at least the interior wall of a flexible plastic pipe, which pipe exhibits high dimensional stability, good recovery performance and good resistance to media, particularly alcoholic media.
Briefly, this object and other objects of the present invention as hereinafter will become more readily apparent can be attained by molding composition which comprises the following constituents:
I. from 40 to 80 parts by weight of a polyamide, and
II. from 60 to 20 parts by weight of a flexible polymer whose main chains essentially consists of carbon atoms, where the parts by weight of I and II total 100, and wherein the composition contains not more than 2% by weight of extractables, measured by extracting the granules with hot 100 percent ethanol under reflux conditions.
In a second embodiment of the invention, a pipe is formed whose at least interior wall structural component is formed from the molding composition of the invention. especially useful for the piping of aqueous, aqueous-alcoholic or purely alcoholic liquids.